VDO Cytec- sleepy computer question

I have a VDO Cytec 10 computer that's in it's 4th summer. I'm having a lot of trouble lately with it not turning on when it should. The clock stays on so it's not the battery, but it doesn't come out of 'standby' mode on its own when I start riding. So what happens is that I start riding after a break and it doesn't register that I'm riding. At some point I'll look down and realize it's still displaying the clock (instead of speed) and hasn't registered anything of what I've done since the break. If I push a button, it essentially wakes up and starts functioning normally until I stop long enough for it to go back into standby.

What's going on? Is it time to retire this computer and get another? I suppose I could train myself to push a button everytime I start from a stop, but the problem is that I often forget (and it's annoying to reach the end of a ride and know that you did significantly more mileage than your computer says).